1. Field of the Invention
The invention relates in general to elevator systems, and more specifically group supervisory strategy for improving service to floors located below the main floor, i.e., basement and subbasement floors.
2. Description of the Prior Art:
In general, group supervisory strategy for controlling a group or bank of elevator cars to serve floor calls in a building deliberately provides preferred service for the main floor and those above it. A car, when assigned to the basement zone, serves down basement floor calls first. It then reverses after the last car call for the down service direction has been served to serve the up basement floor calls. Thus, a prospective passenger placing a call from a floor below the main floor, such as a basement, or subbasement floor, may experience a relatively long wait for service. This low service priority for basement floor calls is acceptable when the majority of the elevator traffic enters the building at the main floor and travels upwardly to destination floors, with the basement floors being used primarily by maintenance personnel. The basic group supervisory strategies of the prior art are modified for buildings which have parking garages below the main floor, or additional street entrances below the main floor, such as by allowing more than one car to be assigned to the basement zone, and/or by allowing a car assigned to the basement zone to by-pass non-timed out floor calls located above the basement zone as it travels to serve the basement zone assignment, when a basement call has timed out.